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The objective of this work is to develop extended release subcutaneous thermo-responsive in situ gel-forming delivery systems using the following commercially available triblock polymers: poly (lac...

It is common practice to use cannulated rats for pharmacokinetic (PK) in-life studies as it yields high quality PK parameter estimation. While offering many benefits, cannulation requires surgery, post-surgical care, and cannula maintenance. As an alternative approach, the strategy of dosing and bleeding rats via the tail vein in a single experiment is technically feasible and theoretically offers many benefits. Unfortunately, however, as reported by F Tse et al. in 1984 (J Pharm Sci 73: https://doi.org/10.1002/jps.2600731128), parallel tail dosing and bleeding is scientifically flawed and yields inaccurate estimation of PK parameters following intravenous administration. The underlying causality of poor data quality has not been addressed in over 35 years. To overcome the technical flaws associated with parallel tail dosing and bleeding, we have developed a Tail-Dose-Bleed (TDB) method as a substitute for use of cannulated rats. Specifically, the method introduces a flush procedure after dosing, uses separate tail veins for dosing and bleeding, and adjusts dosing and sampling to the proximal and distal portions of the tail, respectively. To demonstrate the proof of principle for this TDB technique, several cassette dosing studies were conducted. The performance of the TDB technique is compared in both stand alone and animal crossover studies employing conventional jugular/femoral bleeding and dosing. The poor data via tail dosing and bleeding previously described by Tse et al. are also recapitulated using their described approach. To ensure broad applicability of the TDB technique, data were generated utilizing compounds of diverse physical chemical properties manifesting a range of clearance and/or volume of distribution characteristics. These data demonstrate that the TDB approach yields comparable PK profiles and parameters as compared to conventional femoral dosing / jugular bleeding. Using this newly described TDB procedure, we demonstrate the ability to overcome documented data quality issues when dosing and bleeding via the tail. The TDB technique has numerous operational advantages of reduced study turnaround time and improved cost effectiveness, but most importantly, addresses key animal welfare concerns relevant to institutional animal care and use committees (IACUC). The notable advantage here is reduced animal stress and discomfort by eliminating the need for surgery and recovery. And by consequence, allows for animals to be group housed and re-used without concern for loss of cannula patency. The tail dose and bleed method is simple and appears readily transferable to other laboratories.

For most oral small-molecule projects within drug discovery, the extent and duration of the effect are influenced by the total clearance of the compound; hence, designing compounds with low clearance remains a key focus to help enable sufficient protein target engagement. Comprehensive understanding and accurate prediction of animal clearance and pharmacokinetics provides confidence that the same can be observed for human. During a MERTK inhibitor lead optimization project, a series containing a biphenyl ring system with benzylamine

The aim of the present study was to evaluate and interpret the pharmacokinetic profiles after subcutaneous (s.c.) administration of crystalline AZ’72 nano- and microsuspensions to rodents. Both formulations were injected at 1.5 and 150 mg/kg to rats. For the lower dose, the profiles were similar after s.c. injection but extended as compared to oral administration. The overall exposure was higher for nanoparticles compared with microparticles during the investigated period. For the higher dose, injection of both suspensions resulted in maintained plateaus caused by the drug depots but, unexpectedly, at similar exposure levels. After addition of a further stabilizer, pluronic F127, nanosuspensions showed improved exposure with dose and higher exposure compared to larger particles in mice. Obviously, a stabilizer mixture that suits one delivery route is not necessarily optimal for another one. The differences in peak concentration (Cmax) between nano- and microparticles were mainly ascribed to differences in dissolution rate. Plasma profiles in mice showed curves with secondary absorption peaks after intravenous and oral administration, suggesting hepatic recirculation following both administration routes. This process, together with the depot formulation, complicates the analysis of absorption from s.c. administration, i.e. multiple processes were driving the plasma profile of AZ’72.

The objective of the study was to evaluate the pharmacokinetic profile after different subcutaneous (s.c.) administrations of nano- and microparticle suspensions of griseofulvin to mice. The solubility of the compound was determined as approximately 40 µM, at 37 °C, independent of particle size, stabilizer mixtures investigated and solvent used for measurement. The present in vivo studies demonstrated non-linear absorption kinetics (in peak concentration, Cmax) for griseofulvin up to 50 mg/kg after s.c. administration of nanocrystals and microsuspensions but linear increase in area under the curve (AUC) at all occasions investigated. Cmax was higher for smaller particles administered. Both investigated suspensions, at 10 and 50 mg/kg, showed significantly sustained plasma profiles compared to i.v. and p.o. administration. Administering 10 and 50 mg/kg of griseofulvin nanocrystals as 10 mL/kg, instead of 2.5 mL/kg, improved Cmax but AUC was unchanged. The present study showed that the bioavailability of griseofulvin, administered as nano- and microparticles, increased significantly after s.c. administration (60–100%) compared with p.o. dosing (17%). The drug is currently orally administered and clearly exposed to a significant first pass metabolism, i.e. an ideal candidate for an alternative administration route, like s.c. injection.